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expansion and contraction joints

Who among us has not seen expansion and contraction joints, you may have noticed in huge buildings such as schools, hospitals or factories, or you may have noticed this more clearly in bridges and roads, which is the presence of breaks in these facilities and roads and these are called expansion and contraction joints.

In the world of construction, building construction and paving roads, expansion and contraction joints are important things to pay attention to. They divide the huge facility into two or more parts according to specifications, in order to relieve pressure on building materials caused by the movement of the building and changes in temperature. The movement of masonry in expansion and contraction joints is stimulated mainly by:

Thermal expansion and contraction caused by changes in temperature,

swaying because of the wind

seismic events

static load deflection

Live load deviation

Since expansion and contraction joints divide the entire structure, this denominator is a gap in all building structures – walls; floors, courtyards or divided concourses; Basic floors and walls.

A system of expansion and contraction joints is used to bridge the gap and restore the building’s functionality as a whole and while accommodating the expected movements.

The term ‘moving joint’ has been widely adopted in preference as it more appropriately includes the fact that the movement of the building results in compression and extension of the fastening materials. For example, when the structure is heated, the building material from which it is built expands. This closes the “expansion spacer”

 Concrete expansion and contraction joints reduce concrete cracking and damage while minimizing stress damage and enhancing the performance capabilities of concrete using appropriate combined techniques to accommodate expansion and contraction cycles.

Concrete expands and contracts with changes in temperature and humidity. With an increase in temperature or an increase in the moisture content of concrete, expansion occurs. As the temperature decreases, the concrete will shrink. Providing movement absorption at pre-determined locations with appropriate joint applications prevents the development of stresses that can tear the concrete.

The type of spacer and spacing varies with each project according to the type of structure, climatic conditions, and expected stresses in the concrete.

 Concrete’s coefficient of thermal expansion is 0.0000055 per linear inch of concrete per degree Fahrenheit of temperature change, resulting in movement of approximately 0.66 inches per 100 feet with a temperature range of 100 degrees Fahrenheit (38 degrees Celsius).

To estimate the length of expansion, multiply the length in inches x the number of degrees of the expected temperature difference x 0.0000055.

Use the resulting projected motion to determine the correct thickness of expansion and contraction joints and the appropriate spacing for spacer placement.

 Thin (1/4″, 3/8″, or 1/2) spacers (6.35 mm, 9.53 mm, or 12.7 mm) spaced at frequent intervals provide greater control than thicker joints spaced at greater distances.

 The basic concept is to provide ample space for the concrete to expand and contract without creating harmful stresses and resulting cracking.